Multi-directional binder jetting additive manufacturing

ABSTRACT

The devices, systems, and methods of the present disclosure are directed to powder spreading and binder distribution techniques for consistent and rapid layer-by-layer fabrication of three-dimensional objects formed through binder jetting. For example, a powder may be spread to form a layer along a volume defined by a powder box, a binder may be deposited along the layer to form a layer of a three-dimensional object, and the direction of spreading the layer and depositing the binder may be in a first direction and in a second direction, different from the first direction, thus facilitating rapid formation of the three-dimensional object with each passage of the print carriage over the volume. Powder delivery, powder spreading, thermal energy delivery, and combinations thereof, may facilitate consistently achieving quality standards as the rate of fabrication of the three-dimensional object is increased.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationsNo. 62/488,461, filed on Apr. 21, 2017, the entire contents of which areincorporated herein by reference.

BACKGROUND

Binder jetting is an additive manufacturing technique based on the useof a liquid binder to join particles of a powder to form athree-dimensional object. In particular, a controlled pattern of theliquid binder is applied to successive layers of the powder in a powderbed such that the layers of the powder adhere to one another form athree-dimensional object. The three-dimensional object is then densifiedinto a finished part through subsequent processing, such as sintering.

The binder jetting fabrication process used to form thethree-dimensional objects, however, can present certain challenges withrespect to quality and throughput of finished parts formed from thethree-dimensional objects. In particular, consistent layer-by-layerdistribution of the powder and the liquid binder to form thethree-dimensional object is important for achieving target quality ofthe finished part formed from the three-dimensional object. However, thetime associated with consistent layer-by-layer distribution of thepowder and the liquid binder can have an adverse impact on thecommercial scale viability of binder jetting as an additivemanufacturing technique to form finished parts. Thus, there generallyremains a need for improving speed in the layer-by-layer distribution ofthe powder and liquid binder while maintaining or improving quality ofthree-dimensional objects formed using binder jetting techniques.

SUMMARY

The devices, systems, and methods of the present disclosure are directedto powder spreading and binder distribution techniques for consistentand rapid layer-by-layer fabrication of three-dimensional objects formedthrough binder jetting. For example, a powder may be spread to form alayer along a volume defined by a powder box, a binder may be depositedalong the layer to form a layer of a three-dimensional object, and thedirection of spreading the layer and depositing the binder may be in afirst direction and in a second direction, different from the firstdirection, thus facilitating rapid formation of the three-dimensionalobject with each passage of the print carriage over the volume. Powderdelivery, powder spreading, thermal energy delivery, and combinationsthereof, may facilitate consistently achieving quality standards as therate of fabrication of the three-dimensional object is increased.

According to one aspect, a method of additive manufacturing may include,along a volume defined by a powder box, spreading a layer of powderincluding metal particles, depositing a binder in a controlledtwo-dimensional pattern along the layer, and directing thermal energy tothe layer, wherein the steps of spreading the layer, depositing thebinder, and directing the thermal energy to the layer are performed in afirst direction across the volume and repeated in a second direction,different from the first direction, across the volume to formalternating layers of a three-dimensional object. The second directionmay be, for example, substantially opposite the first direction acrossthe volume.

In certain implementations, directing thermal energy to the layer mayinclude directing the thermal energy to the binder deposited along thelayer. Additionally, or alternatively, directing thermal energy to thelayer may include increasing at least a local temperature of the layer.For example, directing thermal energy to the layer may include drying atleast a portion of the layer. Further, or instead, directing the thermalenergy to the layer may include directing one or more of infrared energyor microwave energy to the layer.

In some implementations, directing thermal energy to the layer mayinclude moving a thermal energy source across the layer, with movementof the thermal energy source indexed relative to spreading sequentiallayers of powder along the volume.

In certain implementations, depositing the binder may include ejectingthe binder from at least one ejection orifice defined by a printcarriage moving in the first direction and in the second direction.

In some implementations, in the first direction, spreading the layer ofpowder may include dispensing a first powder from a first hopper and, inthe second direction, spreading the layer of powder includes dispensinga second powder from a second hopper, the second hopper different fromthe first hopper, and the second powder different from the first powder.For example, the first powder may include metal particles of a firstmetal and the second powder includes metal particles of a second metal,different from the first metal.

In certain implementations, the method may further include depositing ananti-sintering agent along the layer of powder along a portion of thelayer outside of or along the controlled two-dimensional pattern.

According to another aspect, an additive manufacturing system mayinclude a powder box defining a volume, at least one spreader movableover the volume to spread a layer of a powder across the volume, a printcarriage defining at least one ejection orifice, the print carriagemovable over the volume, and the print carriage actuatable to eject abinder from the at least one ejection orifice in a direction toward thelayer as the print carriage moves over the volume, and at least onethermal energy source movable over the volume in coordination withmovement of the at least one spreader over the volume, the at least onethermal energy source positioned to direct thermal energy toward thelayer as the at least one thermal energy source moves over the volume.

In some implementations, the at least one thermal energy source may bemovable over the volume in coordination with movement of the printcarriage to trail the at least one ejection orifice across the volume.Additionally, or alternatively, the at least one thermal energy sourcemay be movable over the volume at a substantially constant rate.Further, or instead, the at least one spreader, the print carriage, andthe at least one thermal energy source may each be movable over thevolume at substantially the same rate as one another. Still further, orinstead, the at least one thermal energy source may include one or moreof an infrared energy source or a microwave energy source.

In certain implementations, the at least one spreader may be movableover the volume in a first direction and in a second direction differentfrom the first direction, and the at least one spreader is positionablerelative to the volume to spread alternating layers of the powderthrough movement in the first direction and in the second direction. Forexample, the at least one spreader may include a first spreader and asecond spreader, the first spreader disposed relative to the secondspreader to precede the second spreader over the volume in the firstdirection, and the second spreader disposed relative to the firstspreader to precede the first spreader over the volume in the firstdirection. Additionally, or alternatively, the at least one thermalenergy source may include a first thermal energy source and a secondthermal energy source, the first thermal energy source trailing thefirst spreader over the volume in the first direction, and the secondthermal energy source trailing the second spreader over the volume inthe second direction.

According to another aspect, an additive manufacturing system mayinclude a print box, a print carriage, a spreader, and a hopper. Theprint box may define a volume, and the print carriage may be movableover the volume, the print carriage defining at least one ejectionorifice directed toward the volume as the print carriage moves over thevolume. The spreader may be movable over the volume in advance of theprint carriage. The hopper may be movable over the volume in advance ofthe spreader, the hopper defining a dispensing region, the hopperincluding a plurality of dispensing rollers along the dispensing region,and the plurality of dispensing rollers rotatable relative to oneanother to move a powder through the dispensing region and toward thevolume in advance of the spreader as the spreader moves toward aposition over the volume to form a layer of the powder, onto which abinder is deliverable from the at least one ejection orifice of theprint carriage trailing the spreader over the volume. Each dispensingroller of the plurality of dispensing rollers may have, for example, asubstantially similar diameter.

In certain implementations, dispensing rollers of the plurality ofdispensing rollers may be spaced apart from one another to define a gap,and the plurality of dispensing rollers are rotatable relative to oneanother to move the powder through the gap and toward the volume. Thedispensing region of the hopper may span a dimension of the volumesubstantially parallel to the gap as the hopper moves over the volume.Additionally, or alternatively, the plurality of dispensing rollers mayspan the dimension of the volume as the hopper moves over the volume.

In some implementations, the additive manufacturing system may furtherinclude at least one motor mechanically coupled to one or moredispensing rollers of the plurality of dispensing rollers, the at leastone motor actuatable to rotate the plurality of dispensing rollersrelative to one another. The at least one motor may be, for example,actuatable to rotate the plurality of dispensing rollers in acounter-rotating direction relative to one another. In certaininstances, the additive manufacturing system may further include acontroller in electrical communication with the at least one motor, thecontroller configured to actuate the at least one motor based onmovement of the hopper over the volume. The controller may beconfigured, for example, to actuate the at least one motor in a firstdirection of movement of the hopper over the volume and to pauseactuation of the at least one motor in a second direction of movement ofthe hopper over the volume, the second direction of movement differentfrom the first direction of movement. Further, or instead, thecontroller may be configured to actuate the at least one motor based onspeed of movement of the hopper over the volume. Additionally, oralternatively, the controller may be configured to actuate the at leastone motor to rotate the plurality of dispensing rollers at substantiallythe same rotation speed.

In certain implementations, the hopper may include a storage region influid communication with the dispensing region, the powder movable fromthe storage region toward the dispensing region through force of gravityas the hopper moves over the volume.

In some implementations, the hopper may include a shutter selectivelymovable between a first position away from the dispensing region to asecond position below the dispensing region to interrupt movement ofpowder exiting the hopper via the dispensing region. The shutter may be,for example, selectively movable between the first position and thesecond position based on rotation of dispensing rollers of the pluralityof dispensing rollers.

According to another aspect, a method of additive manufacturing of anobject may include moving a hopper over a volume defined by a print box,as the hopper moves over the volume, rotating a plurality of dispensingrollers disposed along a dispensing region defined by the hopper, therotation of the plurality of dispensing rollers moving a powder towardthe volume from the dispensing region, spreading the powder along thevolume to form a layer of the powder, and, in a controlledtwo-dimensional pattern, ejecting a binder from at least one ejectionorifice of a print carriage to the layer of the powder to form a portionof the object.

In certain implementations, rotation of the plurality of dispensingrollers may move the powder toward the volume through a gap definedbetween the plurality of dispensing rollers. The gap and the dispensingregion may span a dimension of the volume substantially perpendicular toa direction of movement of the hopper over the volume. Additionally, oralternatively, rotating the plurality of dispensing rollers may includecounter-rotating dispensing rollers of the plurality of dispensingrollers. Further or instead, rotating the plurality of dispensingrollers may include controlling a rotation speed of at least onedispensing roller of the plurality of dispensing rollers based on aspeed of movement of the hopper over the volume. Still further orinstead, rotating the plurality of dispensing rollers may includecontrolling a rotation speed of at least one dispensing roller of theplurality of dispensing rollers based on position of the hopper over thevolume. For example, controlling the rotation speed of the at least onedispensing roller may include reducing the rotation speed of the atleast one dispensing roller as the hopper moves from a first side of thevolume to a second side of the volume, the second side of the volumeopposite the first side of the volume.

In some implementations, rotating the plurality of dispensing rollersmay include rotating each dispensing roller of the plurality ofdispensing rollers at substantially the same rotation speed.

In certain implementations, rotating the plurality of dispensing rollersmay include controlling a rotation speed of each dispensing roller ofthe plurality of dispensing rollers based on a direction of movement ofthe hopper over the volume.

According to yet another aspect, a method of additive manufacturing mayinclude moving at least one roller across a volume defined by a powderbox, movement of the at least one roller across the volume spreading alayer of a powder across the volume, as the at least one roller spreadsthe layer across the volume, vibrating the at least one roller to packthe powder in the volume, and delivering a binder from a print carriageto the layer of the powder in a predetermined two-dimensional patternassociated with the layer as the print carriage moves over the volume.For example, vibrating the at least one roller may include vibrating theat least one roller at a frequency of greater than about 1 kHz or lessthan about 1 MHz.

In some implementations, moving the at least one roller across thevolume may include rotating the at least one roller in a directioncounter to a direction of movement of the at least one roller across thevolume. Additionally, or alternatively, vibrating the at least oneroller may include superimposing rotational vibration of the at leastone roller onto the rotation of the at least one roller. Further orinstead, vibrating the at least one roller may include vibrating the atleast one roller in a direction substantially perpendicular to adirection of movement of the at least one roller across the volume.

In some implementations, the at least one roller may be coupled tosprings, and vibrating the at least one roller includes deliveringspring force to the at least one roller. Further, or instead, the atleast one roller may be coupled to an eccentric motor, and vibrating theat least one roller includes controlling the eccentric motor to apredetermined rotation speed. Additionally, or alternatively, the atleast one roller may be coupled to a voice coil actuator, and vibratingthe at least one roller includes actuating the voice coil actuator at apredetermined frequency.

In certain implementations, the at least one roller may include a walldefining a roller volume, and vibrating the at least one roller includespulsing pressurized fluid in the roller volume to expand the wall as theat least one roller moves across the powder box. The pressurized fluidmay include one or more of a gas (e.g., air) or a liquid (e.g., water).

In some implementations, the at least one roller may include apiezoelectric coating on an outer surface of the at least one roller,and vibrating the at least one roller may include sending a pulsedelectric signal to the piezoelectric coating as the at least one rollermoves across the volume.

In certain implementations, the method may further include, for eachrespective layer of a plurality of layers, repeating the steps of movingthe at least one roller across the volume, vibrating the at least oneroller, and delivering the binder from the print carriage to therespective layer in a predetermined two-dimensional pattern associatedwith the respective layer to form a three-dimensional object.Additionally, or alternatively, one or more of the steps of moving theat least one roller across the volume, vibrating the at least oneroller, and delivering the binder from the print carriage to therespective layer may be carried out in a first direction across thevolume and in a second direction across the volume, and the firstdirection is different from the second direction.

According to yet another aspect, an additive manufacturing method mayinclude moving at least one roller at a predetermined velocity across avolume defined by a powder box, movement of the at least one rolleracross the volume spreading a layer of a powder across the volume,vibrating the at least one roller at a predetermined frequency, thepredetermined frequency corresponding to a wavelength substantiallyequal to an average size of particles of the powder as the at least oneroller moves across the powder box at the predetermined velocity, anddelivering a binder to the layer in a predetermined two-dimensionalpattern corresponding to the layer. As an example, vibrating the atleast one roller may include vibrating the at least one roller at afrequency of about 1 kHz to about 1 MHz.

In certain implementations, moving the at least one roller across thevolume may include rotating the at least one roller in a directioncounter to a direction of movement of the at least one roller across thevolume. Further, or instead, vibrating the at least one roller mayinclude superimposing rotational vibration of the at least one rolleronto the rotation of the at least one roller. Additionally, oralternatively, vibrating the at least one roller may include vibratingthe at least one roller in a direction substantially perpendicular to adirection of movement of the at least one roller across the volume.

In some implementations, the method may further include, for eachrespective layer of a plurality of layers, repeating the steps of movingthe at least one roller, vibrating the at least one roller, anddelivering the binder to the layer of the powder to form athree-dimensional object.

According to still another aspect, an additive manufacturing system mayinclude a powder box, a print carriage, and at least one roller. Thepowder box may define a volume. The print carriage may define at leastone ejection orifice, the print carriage movable over the volume, andthe print carriage actuatable to eject a binder from the at least oneejection orifice in a direction toward a layer of a powder along thevolume as the print carriage moves over the volume. The at least oneroller may be movable over the volume in advance of the print carriageto spread the layer of the powder across the volume, the at least oneroller actuatable to vibrate at a predetermined frequency as the atleast one roller moves over the volume to transmit vibration from the atleast one roller to the powder as the layer is spread across the volume.As an example, the at least one roller may be rotatable in a directioncounter to a direction of movement of the at least one roller across thevolume as the at least one roller moves across the volume. Additionally,or alternatively, the at least one roller is actuatable to vibrate asthe at least one roller is rotated in the direction counter to thedirection of movement of the at least one roller such that vibration ofthe at least one roller is superimposed on counter rotation of the atleast one roller.

BRIEF DESCRIPTION OF THE DRAWINGS

The devices, systems, and methods described herein are set forth in theappended claims. However, for the purpose of explanation, severalimplementations are set forth in the following drawings:

FIG. 1A is a schematic representation of an additive manufacturingsystem for forming a three-dimensional object.

FIG. 1B is a schematic representation of a material carriage of theadditive manufacturing system of FIG. 1A.

FIG. 2 is a bottom view of the print carriage of the additivemanufacturing system of FIG. 1A.

FIG. 3 is a flowchart of an exemplary method of thermal energy deliveryfor additive manufacturing.

FIG. 4 is a flowchart of an exemplary method of dispensing powder foradditive manufacturing.

FIG. 5 is a flowchart of an exemplary method of packing powder foradditive manufacturing.

DESCRIPTION

Embodiments will now be described with reference to the accompanyingfigures. The foregoing may, however, be embodied in many different formsand should not be construed as limited to the illustrated embodimentsset forth herein.

All documents mentioned herein are hereby incorporated by reference intheir entirety. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the terms “or” and “and” shouldeach generally be understood to mean “and/or.”.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,” or thelike, when accompanying a numerical value, are to be construed asindicating a deviation as would be appreciated by one of ordinary skillin the art to operate satisfactorily for an intended purpose. Ranges ofvalues and/or numeric values are provided herein as examples only, anddo not constitute a limitation on the scope of the describedembodiments. The use of any and all examples, or exemplary language(“e.g.,” “such as,” or the like) provided herein, is intended merely tobetter illuminate the embodiments and does not pose a limitation on thescope of the embodiments. No language in the specification should beconstrued as indicating any unclaimed element as essential to thepractice of the embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “up,” “down,” and the like, arewords of convenience and are not to be construed as limiting terms.

As used herein, the term two-dimensional slice should be understood torefer to a cross-sectional segment of a three-dimensional object, withthe cross-sectional segment having a small thickness (e.g., greater thanabout 40 microns and less than about 150 microns) in a third dimension.That is, the thickness of the two-dimensional slice may be substantiallysmaller than either dimension of the cross-sectional segment in theother two dimensions. In general, two-dimensional slices may be formedon top of one another to form a three-dimensional object.

For the sake of clarity and completeness of explanation, the descriptionthat follows describes the use of devices, systems, and methods in thecontext of multi-directional binder jetting—that is, binder jettingfabrication techniques in which layers of powder are spread in at leasttwo different directions in the course of fabricating athree-dimensional object and, additionally or alternatively, binder isapplied to layers from a print carriage moving over a volume in at leasttwo different directions. However, unless otherwise specified or madeclear from the context, the description of devices, systems, and methodswith respect to multi-directional binder jetting herein should not beunderstood to preclude the use of such devices, systems, and methods inthe degenerate case of binder jetting along only a single direction.Thus, for example, while devices, systems, and methods for directingthermal energy, dispensing powder, and packing powder are describedherein with respect to multi-directional binder jetting, such devices,systems, and methods should be understood to be beneficially applicableto single-direction binder jetting, unless otherwise indicated or madeclear from the context.

Referring now to FIGS. 1A, 1B, and 2 , an additive manufacturing system100 may include a print box 102, a first material carriage 104 a, asecond material carriage 104 b, and a print carriage 106. The print box102 may define a volume 108 in which, as described in greater detailbelow, a three-dimensional object 110 may be formed by jetting a binder112 (e.g., a polymeric binder) along layers of powder 120 (e.g., apowder including inorganic particles, such as metal particles, ceramicparticles, or a combination thereof) spread in the volume 108. Morespecifically, each instance of the first material carriage 104 a and thesecond material carriage 104 b may include a respective instance of aspreader 114 and a respective instance of a hopper 116. Each instance ofthe spreader 114 may extend from the respective instance of the firstmaterial carriage 104 a and the second material carriage 104 b towardthe volume 108 as the respective material carriage moves over the volume108 and, further or instead, each instance of the hopper 116 may definea respective instance of a dispensing region 118 directed toward thevolume 108 to dispense a quantity of a powder 120 to the volume 108. Theprint carriage 106 may define at least one ejection orifice 202positioned to direct a fluid, such as the binder 112, toward the powder120 in the volume 108. As described in greater detail below, the firstmaterial carriage 104 a, the print carriage 106, and the second materialcarriage 104 b may each be movable over the volume 108 to carry outmulti-directional binder jetting fabrication according to any one ormore of the methods described herein. In general, such multi-directionalbinder jetting carried out by the additive manufacturing system 100 maysignificantly increase the rate of fabrication of three-dimensionalobjects, as compared to binder jetting in only a single direction. Asalso described in greater detail below, the additive manufacturingsystem 100 may carry out any one or more of various different powderdelivery, powder spreading, thermal energy delivery techniques describedherein to address challenges associated with achieving quality standardsof the three-dimensional object 110 as the rate of fabrication isincreased through multi-directional printing.

In general, the spatial orientation of the first direction and thesecond direction of movement of the first material carriage 104 a, thesecond material carriage 104 b, and the print carriage 106 relative toone another may be any of various different combination of directionsuseful for achieving efficient movement of components as two-dimensionalslices of the three-dimensional object 110 are formed in alayer-by-layer fabrication process. Thus, in a particularly usefulimplementation, the first direction and the second direction may besubstantially opposite one another over the volume 108 such that thecomponents move back and forth over the volume 108 as thethree-dimensional object 110 is formed. As compared to other directionsof movement, this type of back and forth movement may offer advantagesassociated with the rate of fabrication. Further, or instead, back andforth movement may reduce the complexity of controlling timing andposition of the first material carriage 104 a, the second materialcarriage 104 b, and the print carriage 106 relative to one anotherand/or relative to the volume 108, with corresponding advantages beingrealized in accuracy of the three-dimensional object 110.

In certain implementations, the additive manufacturing system 100 mayinclude one or more rails 122, which may be useful for controllingtiming and positioning of one or more of the first material carriage 104a, the second material carriage 104 b, or the print carriage 106throughout multi-directional binder jetting to form thethree-dimensional object 110. For example, the first material carriage104 a, the second material carriage 104 b, the print carriage 106, or acombination thereof, may be bidirectionally movable along the one ormore rails 122 to move back and forth over the volume 108. As therespective components undergo back and forth movement along the one ormore rails 122, it should be appreciated that the shape and position ofthe one or more rails 122 relative to the volume 108 supports the firstmaterial carriage 104 a, the second material carriage 104 b, the printcarriage 106, or a combination thereof, at one or more controlleddistances relative to the volume 108. As a specific example, the one ormore rails 122 may be substantially parallel to the volume 108 at leastalong a portion of the one or more rails 122 corresponding to travel ofthe first material carriage 104 a, the second material carriage 104 b,the print carriage 106, or a combination thereof, over the volume 108.In certain instances, the one or more rails 122 may be dimensioned to besubstantially rigid in response to forces exerted on the one or morerails 122 through movement of the first material carriage 104 a, thesecond material carriage 104 b, the print carriage, or a combinationthereof, along the one or more rails 122 such that the one or morecontrolled distances are substantially maintained throughout themovement of the respective components along the one or more rails 122.Additionally, or alternatively, in instances in which the first materialcarriage 104 a, the second material carriage 104 b, and the printcarriage 106 are movable on the same one or more rails 122, the one ormore rails 122 may advantageously provide a robust mechanism formaintaining the components in a fixed physical orientation relative toone another as the components move back and forth over the volume 108.

In general, the timing of the respective movements the first materialcarriage 104 a, the second material carriage 104 b, and the printcarriage 106 may be controlled according to any of various differenttechniques suitable for achieving accurate and rapid formation of thethree-dimensional object 110 through multi-directional binder jetting.Thus, in some implementations, one or more of the first materialcarriage 104 a, the second material carriage 104 b, and the printcarriage 106 may be independently movable relative to one another overthe volume 108 in the first direction and in the second direction. Suchindependent movement may be useful, for example, for reducing thelikelihood of contaminating or otherwise degrading performance of theprint carriage 106 through exposure to the powder 120 being dispensedfrom the first material carriage 104 a in the first direction and fromthe second material carriage 104 b in the second direction. As anexample, one or more of the first material carriage 104 a, the printcarriage 106, and the second material carriage 104 b may be movable overthe volume 108 one at a time as the other components are disposed alongone or more sides of the volume 108. Additionally, or alternatively, oneor more of the first material carriage 104 a, the second materialcarriage 104 b, and the print carriage 106 may be mechanically coupledto at least another one of the first material carriage 104 a, the secondmaterial carriage 104 b, and the print carriage 106 to move as a singleunit in the first direction and the second direction over the volume108. That is, while the first material carriage 104 a, the secondmaterial carriage 104 b, and the print carriage 106 are described anddepicted as separate components, any one or more of the features of thefirst material carriage 104 a, the second material carriage 104 b, andthe print carriage 106 may be combined into a single unit. As comparedto moving each component over the volume 108 one at a time, such asingle unit may advantageously reduce delays and control complexity thatmay be associated with moving the first material carriage 104 a, thesecond material carriage 104 b, and the print carriage 106bidirectionally across the volume 108.

In general, the first material carriage 104 a and the second materialcarriage 104 b may be substantially identical to one another, exceptthat each is generally a mirror configuration of the other with respectto at least one plane extending through the print carriage 106. Thissymmetry of the first material carriage 104 a and the second materialcarriage 104 b may be particularly advantageous for achievingsubstantially similar layer characteristics in each direction of thebinder jetting process carried out by the additive manufacturing system100. In turn, such similar layer characteristics may facilitate formingthe three-dimensional object 110 within target dimensional tolerances.That is, the three-dimensional object 110 may be formed substantiallywithout defects associated with changing direction of the layer-by-layerfabrication process. Accordingly, for the sake of clarity and efficientdescription, the features of the first material carriage 104 a aredescribed below and, unless another intention is indicated,corresponding aspects of the second material carriage 104 b shall beunderstood to be identical to those of the first material carriage 104 aand are not described separately.

The hopper 116 may define a storage region 124 in fluid communicationwith the dispensing region 118 such that the powder 120 is movable(e.g., through the force of gravity, through the use of actuators, or acombination thereof) from the storage region 124 to the volume 108 viathe dispensing region 118. The storage region 124 may store, forexample, a quantity of the powder 120 sufficient for forming multiplelayers of the three-dimensional object 110. As a competingconsideration, however, the capacity of the storage region 124 may belimited by space and weight considerations associated with rapidmovement of the hopper 116 in some applications.

To facilitate management of moisture in the quantity of the powder 120stored in the storage region 124, each of the first material carriage104 a and the second material carriage 104 b may include a heater 126 inthermal communication with the storage region 124 of the hopper 116. Theheater 126 may be any of various different types of heaters known in theart and, thus, may include a resistance heater. In some instances, theheater 126 may be adjustable to maintain the powder 120 in the storageregion 124 at a predetermined temperature, such as a predeterminedtemperature provided by an operator of the machine.

Additionally, or alternatively, to facilitate management of settling ofthe powder 120 stored in the storage region 124, each of the firstmaterial carriage 104 a and the second material carriage 104 b mayinclude an agitator 128 in mechanical communication with the storageregion 124 of the hopper 116. In general, the agitator 128 may vibratewalls of the storage region 124 at frequencies that are useful forreducing the likelihood of the powder 120 sticking to the walls of thestorage region 124 while not interfering with overall movement of thehopper 116 across the volume 108. By way of example, the agitator 128may include a piezoelectric element actuatable to vibrate the storageregion 124.

The dispensing region 118 of the hopper 116 may span a width of thevolume 108. As used in this context, the width of the volume 108 mayinclude, for example, a dimension of the volume 108 substantiallyperpendicular to the first direction and the second direction as thedispensing region 118 moves back and forth over the volume 108 in thefirst direction and the second direction. With the dispensing region 118spanning the width of the volume 108, the powder 120 may be dispensedalong the entire width of the volume 108 as the hopper 116 moves overthe volume 108. As compared to other patterns of distribution of thepowder 120, distributing the powder 120 along the entire width of thevolume 108 may facilitate achieving a substantially uniform distributionof the powder 120 as the hopper 116 moves rapidly over the volume 108.

The hopper 116 may include, in some instances, a shutter 129 movablebetween an open position (shown in FIGS. 1A and 1B) and a closedposition. In the open position, the shutter 129 may be spaced away fromthe dispensing region 118 of the hopper 116 such that the powder 120exiting the dispensing region 118 is substantially unobstructed by theshutter 129. In the closed position, the shutter 129 may slide over thedispensing region 118 to at least partially obstruct the dispensingregion 118 of the hopper 116 to block the powder 120 from the hopper 116from inadvertently falling out of the hopper 116. Thus, controlling theshutter 129 between the open position and the closed position may beuseful for reducing errant distribution of the powder 120 and, thus, mayfacilitate accurately forming the three-dimensional object 110.

The shutter 129 may be in the open position as the hopper 116 of a givenone of the first material carriage 104 a and the second materialcarriage 104 b moves in a leading position over the volume 108, thuspermitting the powder 120 from the leading instance of the hopper 116 tobe directed toward the volume 108. The shutter 129 may be in the closedposition as the hopper 116 of a given one of the first material carriage104 a and the second material carriage 104 b moves in a trailingposition over the volume 108, thus blocking the powder 120 from thetrailing instance of the hopper 116 to be blocked from falling onto thevolume 108. Thus, as a specific example, the shutter 129 of the hopper116 associated with the first material carriage 104 a may be in the openposition as the first material carriage 104 a precedes the printcarriage 106 over the volume 108 while the shutter 129 of the hopper 116associated with the second material carriage 104 b may be in the closedposition as the second material carriage 104 b trails the print carriage106 over the volume 108. In the reverse direction, the positions of therespective instances of the shutter 129 may be reversed.

In certain implementations, as the shutter 129 is switched from theclosed position to the open position, a small amount of the powder 120may fall from the dispensing region 118 of the hopper 116 in a mannerthat may be uncontrolled or, further or instead, in a quantity that isunpredictable. Thus, to reduce the likelihood of this small amount ofthe powder 120 may interfere with accurately forming thethree-dimensional object 110, the shutter 129 may be switched from theclosed position to the open position along at a position in which thedispensing region 118 is lateral to the volume 108 such that the smallamount of the powder 120 may be dumped prior to moving the dispensingregion 118 over the volume 108 to dispense the powder 120 to be formedinto a layer along a top portion of the volume 108.

In general, the shutter 129 may be moved between the open position andthe closed position according to any one or more of various differentmechanical and/or electrical actuating mechanisms. Thus, for example,the shutter 129 may slide between the open position and the closedposition through an electrically controlled actuator (not shown). Whilethe shutter 129 has been described as sliding between the open positionand the closed position, it should be appreciated that other types ofmovement of the shutter 129 may be additionally or alternativelyimplemented to control the flow of the powder 120 from the dispensingregion 118. For example, the shutter 129 may be pivotable about a hingeto move between the open and closed position.

In certain implementations, the additive manufacturing system 100 mayinclude a bulk powder source 130, which may be useful for addressingcertain challenges associated with moving the hopper 116 over the volume108 as part of a multi-directional binder jetting process. For example,the bulk powder source 130 may be sized to contain enough powdersufficient to form one or more instances of the three-dimensional object110. The hopper 116 may be positionable relative to the bulk powdersource 130 to receive the powder 120 from the bulk powder source 130(e.g., under the force of gravity). In certain instances, the hopper 116may be refilled during the course of fabrication of thethree-dimensional object 110, which may be particularly useful forforming the storage region 124 of the hopper 116 with a volume suitablefor moving over the volume 108. That is, because the hopper 116 may berefilled, the storage region 124 may be formed with a relatively smallvolume such that the size and weight of the hopper may be suitable forrapid movement over the volume 108.

In general, the spreader 114 may be positioned on the respectiveinstance of the first material carriage 104 a and the second materialcarriage 104 b such that the spreader 114 trails the dispensing region118 of the hopper 116 as the dispensing region 118 precedes the at leastone ejection orifice 202 of the print carriage 106 over the volume 108.Thus, as the powder 120 is dispensed from the dispensing region 118 ofthe hopper 116 to the volume 108, the spreader 114 may move over thevolume 108 at a substantially fixed distance to spread the powder 120into a layer. In turn, the binder 112 may be distributed from the atleast one ejection orifice 202 onto the layer in a controlledtwo-dimensional pattern corresponding to a respective two-dimensionalslice of the three-dimensional object 110.

In certain instances, a height of the spreader 114 above the volume 108may be adjustable. For example, the height of the spreader 114 above thevolume 108 may be adjustable to achieve a target layer height as thespreader 114 moves over the volume 108 in a direction in advance of theat least one ejection orifice 202 of the print carriage 106.Additionally, or alternatively, the height of the spreader 114 may beadjustable to move the spreader 114 away from the volume 108 as thespreader 114 moves over the volume 108 in a direction trailing the atleast one ejection orifice 202 of the print carriage 106. Continuingwith this example, such selective movement of the spreader 114 away fromthe volume 108 may be useful, for example, for reducing the likelihoodof unintended contact between the spreader 114—in the trailingposition—and the powder 120 which, in turn, may reduce the likelihood ofintroducing errors into the three-dimensional object 110 being formed.

The spreader 114 may generally include any manner and form of elongateelement useful for spreading the powder 120 substantially uniformlyacross the volume 108 as the spreader 114 moves over the volume 108.Further, or instead, the spreader 114 may be a unitary body, such as maybe useful for reducing the likelihood of forming debris as the spreader114 spreads the powder 120 repeatedly over the course of formingmultiple instances of the three-dimensional object 110. Thus, forexample, the spreader 114 may be a roller. As used in the context of thespreader 114, a roller should be understood to include, for example, asubstantially cylindrical shape actively and/or passively rotatableabout the elongate axis of the cylindrical shape. For example, theroller may be driven to rotate in a direction substantially opposite adirection of travel of the spreader 114 over the volume 108. As usedherein, movement of the roller in the direction substantially oppositethe direction of travel of the spreader 114 should be understood toinclude rotation of the roller in a direction opposite to a direction offree rotation of the roller in the absence of the applied rotationalforce as the spreader 114 moves over the volume 108 with the roller incontact with the powder 120. As compared to passive rotation of theroller and/or active rotation of the roller in the direction of travelof the spreader 114, rotating the roller in the direction substantiallyopposite the direction of travel of the spreader 114 may produce a moreeven distribution of the powder 120 in the layer formed by the spreader114.

In general, the print carriage 106 may be selectively actuatable (e.g.,electrically actuatable) to produce a controlled distribution of thebinder 112 in a two-dimensional pattern associated with thetwo-dimensional slice of the three-dimensional object 110 being formed.Given that the two-dimensional pattern may be different for differenttwo-dimensional slices, the print carriage 106 may produce varyingpatterns of the binder 112 as required for the layer-by-layerfabrication of the three-dimensional object. These varying patterns maybe produced according to any of various different techniques known inthe art of ink jet printing. Thus, for example, the print carriage 106may include at least one print bar. In turn, each print bar may includea plurality of print heads (e.g., piezoelectric print heads), and eachprint head may define at least one of the plurality of ejectionorifices. Each print head may be independently controllable relative toeach of the other print heads to facilitate accurate delivery of thebinder according to a given controlled two-dimensional patternassociated with a two-dimensional slice being formed as the printcarriage 106 moves across the volume 108.

The at least one ejection orifice 202 may be shaped and arrangedaccording to any of various different patterns useful for producing asuitable distribution of the binder 112 in a controlled two-dimensionalpattern along the layer. For example, the at least one ejection orifice202 may include a plurality of instances of the at least one ejectionorifice 202, and each instance of the at least one ejection orifice 202may be substantially similar to each other instance of the at least oneejection orifice 202. Such similarity between instances of the at leastone ejection orifice may be useful, for example, for producing uniformdistributions of the binder 112. Further, or instead, the at least oneejection orifice 202 may include a plurality of orifices spaced relativeto one another to span one or more dimensions along the top of thevolume 108, with such spatial distribution contributing advantageouslyto uniformity of binder distribution. As an example, the at least oneejection orifice 202 may include a plurality of orifices spaced relativeto one another along a direction substantially perpendicular to an axisdefined by back and forth movement of print carriage 106 over the volume108 in a first direction and a second direction opposite one another.

In certain implementations, the print carriage 106 may be advantageouslyformed to have substantially similar performance in the differentdirections of movement associated with a multi-directional binderjetting process. As an example, the at least one ejection orifice 202may be directed relative to the volume 108 to eject the binder 112 in adirection substantially perpendicular to the volume 108 as the printcarriage moves over the volume 108. This orientation of the at least oneejection orifice 202 may be useful, for example, for jetting the binder112 in a manner that is substantially independent of the direction ofmovement of the print carriage 106 as the binder 112 is jetted towardthe volume 108. In turn, eliminating or at least reducing directionalartifacts associated with directing the binder 112 toward the volume 108may result in improvements in accuracy of the three-dimensional object110 being formed.

The print carriage 106 may, in certain instances, define a plurality ofgas assist orifices 204 positioned relative to the at least one ejectionorifice 202 to limit the impact of errant material on the formation ofthe three-dimensional object 110. For example, the gas assist orifices204 may be disposed on either side of a plane bisecting the at least oneejection orifice 202. That is, the gas assist orifices 204 may bepositioned to precede and trail the at least one ejection orifice 202 asthe print carriage 106 moves across the volume 108 in a first directionand in a second direction different from the first direction. A gas(e.g., air) may be expelled through the plurality of gas assist orifices204 as the binder 112 is ejected from the at least one ejection orifice202. Expelling gas through the plurality of gas assist orifices 204 inthis way may be useful, for example, for reducing the presence of finepowder particles, satellite droplets of the binder 112, or both, abovethe volume 108. Additionally, or alternatively, gas may be suctionedthrough the plurality of gas assist orifices 204 as the binder 112 isejected from the at least one ejection orifice 202. Such suction may, incertain instances, be useful for reducing the presence of satellitedroplets of the binder 112, fine particles, or both, floating above thevolume 108. In general, reducing satellite droplets of the binder 112,fine powder particles, or both, above the volume may reduce thelikelihood of such material interfering with the placement of the binder112 in a controlled two-dimensional pattern on a layer of the powder 120and, thus, may facilitate more accurate formation of thethree-dimensional object 110.

In certain implementations, the additive manufacturing system 100 mayinclude a z-stage actuator 132, which may be mechanically coupled (e.g.,directly mechanically coupled) to a bottom surface 131 of the print box102. Through actuation of the z-stage actuator 132, the bottom surface131 of the print box 102 may be moved in a direction away from the printcarriage 106 to increase a depth dimension of the volume 108 as thethree-dimensional object 110 is formed in the volume 108. In general,the z-stage actuator 132 may be any of various different types of knownmechanical actuators useful for precisely controlled verticaltranslation.

For example, the z-stage actuator 132 may be moveable to move the bottomsurface 131 of the print box 102 by a distance of about the thickness ofeach layer (e.g., about 40 microns to about 150 microns) with each passof the print carriage 106 over the volume 108.

The z-stage actuator 132 may be, for example, releasably coupled to theprint box 102. For example, the z-stage actuator 132 may be decoupledfrom the print box 102 to facilitate removal of the print box 102 fromthe additive manufacturing system 100 once the three-dimensional object110 has been formed in the volume. For example, the print box 102 may besupported on a cart or other similar structure including a plurality ofwheels. Continuing with this example, upon decoupling the print box 102from the z-stage actuator 132, the cart may be rolled to move the printbox 102 to one or more post-processing stations, where excess powder maybe removed from the three-dimensional object 110 and/or thethree-dimensional object 110 may undergo densification into a finalpart. It should be appreciated that the use of a cart or other similarwheeled structure may facilitate, for example, rapidly replacing theprint box 102 as part of a process for rapidly fabricating multipleinstances of the three-dimensional object 110.

The additive manufacturing system 100 may include at least one motor 139coupled to one or more of the first material carriage 104 a, the secondmaterial carriage 104 b, and the print carriage 106 to move eachrespective component over the volume 108 in the first direction and thesecond direction. For example, in instances in which the first materialcarriage 104 a, the second material carriage 104 b, and the printcarriage 106 are bidirectionally movable over the volume 108 along oneor more rails 122, the at least one motor 139 may include a linearactuator, which may be particularly useful for precisely controllingposition of the respective components. More generally, however, the atleast one motor 139 may be any of various different types of motorselectrically controllable to move the first material carriage 104 a, thesecond material carriage 104 b, and the print carriage 106 to carry outany one or more of the various different techniques described herein.

The additive manufacturing system 100 may include a controller 140. Thecontroller may be in electrical communication with one or more of the atleast one motor 139, the first material carriage 104 a, the secondmaterial carriage 104 b, and the print carriage 106, the z-stageactuator 132, and the at least one motor 139. The controller 140 mayinclude one or more processors 141 operable to control the at least onemotor 139, the first material carriage 104 a, the second materialcarriage 104 b, and the print carriage 106 to form the three-dimensionalobject 110.

The additive manufacturing system 100 may, additionally oralternatively, include a non-transitory, computer readable storagemedium 142 in communication with the controller 140 and having storedthereon a three-dimensional model 143 and instructions for causing theone or more processors 141 to carry out any one or more of the methodsdescribed herein. In certain implementations, the controller 140 mayretrieve the three-dimensional model 143 in response to user input andgenerate machine-ready instructions for execution by the additivemanufacturing system 100 to fabricate the three-dimensional object 110.

In use, as the first material carriage 104 a moves over the volume 108,a quantity of the powder 120 may be dispensed from the dispensing region118 of the first material carriage 104 a toward the volume 108 (e.g.,directly onto the volume 108 or toward an area immediately adjacent tothe volume 108). The spreader 114 of the first material carriage 104 amay spread the dispensed quantity of the powder 120 to form a layeralong the top of the volume 108 as the first material carriage 104 amoves over the volume 108. The print carriage 106 may follow the firstmaterial carriage 104 a in the first direction, and the binder 112 maybe ejected from the at least one ejection orifice 202 of the printcarriage 106 toward the layer in a controlled two-dimensional patterncorresponding to a respective two-dimensional slice of thethree-dimensional object 110 being formed. Along the controlledtwo-dimensional pattern, the binder 112 may generally adhere to theparticles of the powder and to one or more adjacent layers. The secondmaterial carriage 104 b may follow the print carriage 106 in the firstdirection and, in this trailing position, the spreader 114 of the secondmaterial carriage 104 b may be in a raised position, out of contact withthe layer, to reduce the likelihood of distorting the controlledtwo-dimensional pattern of the binder 112 in the layer.

Continuing with this example, the order of movement of the secondmaterial carriage 104 b, the print carriage 106, and the first materialcarriage 104 a may then be reversed to form a second layer. Morespecifically, the second material carriage 104 b may move across thevolume 108 in a second direction different from the first direction, anda quantity of the powder 120 may be dispensed from the dispensing region118 of the second material carriage 104 b toward the volume 108 (e.g.,onto the volume 108 or to an area immediately adjacent to the volume108). The spreader 114 of the second material carriage 104 b, in alowered position, may spread the powder 120 along the volume 108 to formthe second layer of the powder 120. As the print carriage 106 followsthe second material carriage 104 b across the volume 108, the printcarriage 106 may eject the binder 112 toward the layer in a controlledtwo-dimensional pattern corresponding to a respective two-dimensionalslice of the three-dimensional object 110 being formed. Along thecontrolled two-dimensional pattern, the binder 112 may adhere theparticles of the powder 120 to each other and to at least one otheradjacent layer. The first material carriage 104 a may follow the printcarriage in the second direction, with the spreader 114 of the firstmaterial carriage 104 a in a raised position above the volume 108 toreduce the likelihood of interfering with the layer formed by the secondmaterial carriage 104 b. Thus, movement of the first material carriage104 a, the print carriage 106, and the second material carriage 104 bacross the volume 108 may be alternated in two different directions toform two-dimensional slices of the three-dimensional object 110 in eachdirection of travel. With less wasted motion, as compared to asingle-direction approach requiring repositioning of components betweenformation of each slice, the additive manufacturing system 100 maysignificantly reduce the rate of fabrication of the three-dimensionalobject 110.

In general, increases in fabrication rate associated with binder jettingprocesses—whether multi-direction or single-direction—may be in tensionwith quality and accuracy goals associated with the fabrication process.That is, as the rate of fabrication increases, challenges associatedwith one or more of binder placement, powder dispensing, and spreadingmay become more pronounced. Accordingly, in the disclosure that follows,certain techniques are described for maintaining accuracy as fabricationrates are increased. More specifically, these techniques are related tothermal energy delivery, powder dispensing, and powder packing to reduceor eliminate certain sources of inaccuracy that may become moresignificant as fabrication rates increase. Unless otherwise specified ormade clear from the context, these techniques should be understood to beequally applicable to single-direction binder jetting andmulti-directional binder jetting.

Thermal Energy Delivery

In some implementations, the additive manufacturing system 100 mayinclude at least one instance of a thermal energy source 144 movable thevolume 108 in coordination with movement of the spreader 114 over thevolume. In general, as the thermal energy source 144 moves over thevolume 108, the thermal energy source 144 may be positioned to directthermal energy toward the volume 108. The thermal energy may be directedthrough the space between the thermal energy source 144 and a layer ontop of the volume 108 according to any manner and form of heat transfer(e.g., convection, conduction, radiation, or a combination thereof),unless otherwise specified or made clear from the context. Thus, forexample, the thermal energy source 144 may be an infrared energy source,a microwave energy source, or a combination thereof.

The first material carriage 104 a and the second material carriage 104 bmay each include a respective instance of the thermal energy source 144such that the thermal energy source 144 is in a substantially fixedorientation relative to the spreader 114 of the respective materialcarriage. In general, the thermal energy source 144 may precede or trailthe spreader 114 over the volume 108, depending on whether applicationof thermal energy to the volume 108 is intended to occur before or afterspreading occurs. Similarly, the thermal energy source 144 may precedeor trail the at least one ejection orifice 202 of the print carriage 106over the volume 108, depending on whether application of thermal energyto a given layer on top of the volume 108 is intended to occur before orafter the binder 112 has been delivered to the given layer. For example,in some instances, the thermal energy source 144 may be positioned suchthat thermal energy is directed to the layer of the powder 120 on top ofthe volume 108 after the binder 112 has been applied in a controlledtwo-dimensional pattern and before a subsequent layer of the powder 120is spread across the volume 108. Timing the application of the thermalenergy in this way may accelerate drying of the binder 112 which, inturn, may reduce the likelihood of smearing or otherwise distorting thecontrolled two-dimensional pattern of the binder 112 in a given layer ontop of the volume 108 as a subsequent layer is formed in a rapidfabrication process. As a specific example, a first instance of thethermal energy source 144 may trail the instance of the spreader 114 ofthe first material carriage 104 a over the volume 108 in a firstdirection, and a second instance of the thermal energy source 144 maytrail the instance of the spreader 114 of the second material carriage104 b over the volume 108 in a second direction opposite the firstdirection. In this configuration, the second instance of the thermalenergy source 144 may direct thermal energy toward the volume 108 as thesecond material carriage 104 b moves in the first direction, trailingthe print carriage 106. Similarly, the first instance of the thermalenergy source 144 may direct thermal energy toward the volume 108 as thefirst material carriage 104 a moves in the second direction, trailingthe print carriage 106.

In general, the effectiveness of the thermal energy source 144 indelivering thermal energy to the volume 108 may be a function of therate of movement of the thermal energy source 144 over the volume 108.That is, for a given rate of thermal energy production, slower speeds ofmovement of the thermal energy source 144 over the volume 108 may resultin more effective heat transfer to the layer on top of the volume 108.Thus, in some instances, the thermal energy source 144 may be adjustableto produce more thermal power as the speed of the thermal energy source144 increases over the volume 108. Additionally, or alternatively, thethermal energy source 144 may be moved over the volume 108 at asubstantially constant rate, which may facilitate transferring apredictable and consistent amount of thermal energy to the layer on topof the volume 108. Further, or instead, the spreader 114, the printcarriage 106, and the thermal energy source 144 may each be movable overthe volume 108 at substantially the same rate as one another, which maybe useful for coordinating heat transfer with the other processesassociated with formation of the three-dimensional object 110.

FIG. 3 is a flowchart of an exemplary method 300 of thermal energydelivery in multi-directional additive manufacturing. In general, unlessotherwise specified or made clear from the context, the exemplary method300 may be carried out using any one or more of the additivemanufacturing systems described herein. Thus, for example, one or moresteps of the exemplary method 300 may be carried out by the additivemanufacturing system 100 (FIG. 1A).

As shown in step 302, the exemplary method 300 may include spreading alayer of powder across a volume defined by a print box. The powder maybe any one or more of the powders described herein and, thus, mayinclude metal particles having a composition suitable for forming afinished part according to predetermined material specifications. Forexample, the metal particles may include one or more components ofstainless steel such that, through densification and/or otherpost-processing, a finished part of stainless steel is formed. Stillfurther or instead, spreading the layer of powder may include spreadingaccording to any one or more of the spreading techniques describedherein. As an example, spreading the layer of powder may include rollingthe powder to form a substantially uniform layer across the volume.

As shown in step 304, the exemplary method 300 may include depositing abinder in a controlled two-dimensional pattern along the layer. Thebinder may be any one or more binders known in the art and suitable foradhering the metal particles of the powder to one another and toadjacent layers to hold the shape of the three-dimensional object beingformed as a green part in the volume. The binder may be removable fromthe three-dimensional object through subsequent processing, such asprocessing to densify the three-dimensional object in instances in whichdensification of the three-dimensional object is desirable. Unlessotherwise specified or made clear from the context, depositing thebinder in the controlled two-dimensional pattern along the layer may beachieved using any one or more of the techniques. Thus, morespecifically, the binder may be deposited along the layer throughejection from a print carriage moving over the volume (e.g., the printcarriage 106 in FIG. 1A).

As shown in step 306, the exemplary method may include directing thermalenergy to the layer. Directing thermal energy to the layer may includeincreasing at least a local temperature of the layer and, in someinstances, may include substantially uniformly increasing thetemperature of the layer. Further, or instead, directing thermal energyto the layer may include directing thermal energy to the layer to dry atleast a portion of the layer. As used in this context, drying should beunderstood to include evaporating at least one liquid from at least aportion of the layer. As an example, the thermal energy may be appliedto the layer (e.g., substantially uniformly) to remove water contentthat may be present in the layer. Additionally, or alternatively, thethermal energy may be directed to portions of the layer on which thebinder is deposited. Directing thermal energy to the binder in the layermay, for example, accelerate drying the binder, which may reduce thelikelihood of deformation of the pattern of the binder as a subsequentlayer of powder is formed on top of the binder as part of alayer-by-layer fabrication process. More generally, directing thermalenergy to the binder may be useful for changing one or morephysicochemical properties of the binder. As used in this context, achange in physicochemical properties of the binder may include, forexample, a change useful for forming the three-dimensional object as astronger green part and/or for improving quality of the final partformed from the three-dimensional object.

In certain instances, directing thermal energy to the layer includesdirecting thermal energy to the layer from a thermal energy sourcemoving over the layer. The movement of the thermal energy source overthe layer may be indexed relative to spreading a subsequent, sequentiallayer along the volume such that the thermal energy is directed to thelayer before the subsequent, sequential layer is formed on top of thelayer. The thermal energy source may be any one or more of the thermalenergy sources described herein and, thus, may include any one or moreof an infrared energy source (to direct infrared energy to the layer) ora microwave energy source (to direct microwave energy to the layer).

As shown in step 308, the exemplary method 300 may include depositing ananti-sintering agent along the layer. In certain instances, theanti-sintering agent may be deposited along the layer by a printcarriage moving over the layer. That is, a print carriage, such as theprint carriage 106, may deliver the anti-sintering agent and the binder(e.g., through different ejection orifices) as the print carriage movesover the layer. As used in this context, an anti-sintering agent shouldbe understood to include a material that is less sinterable than atleast a portion of the metal particles of the powder. By way of example,the anti-sintering agent may be used to introduce certain structuralcharacteristics into a final part formed from the three-dimensionalobject. Such structural characteristics may include an area of weaknessuseful for separating portions of the final part from one another.

As shown in step 310, the exemplary method 300 may include repeating oneor more of the steps of spreading the layer (step 302), depositing thebinder (step 304), directing the thermal energy to the layer (step 306),or depositing the anti-sintering agent along the layer (step 308) untilthe three-dimensional object is complete. More specifically, theexemplary method may include performing one or more of the steps ofspreading the layer (step 302), depositing the binder (step 304),directing thermal energy to the layer (306), or depositing theanti-sintering agent along the layer (step 308) in a first directionacross the volume and repeating the respective steps in a seconddirection, different from the first direction, across the volume to formalternating layers of a three-dimensional object. Unless otherwisespecified or made clear from the context, these steps may be repeated inthe first direction and the second direction using the multi-directionalmovement of hardware according to any one or more of the techniquesdescribed herein. For example, depositing the binder may includeejecting the binder from at least one ejection orifice defined by aprint carriage moving in the first direction and in the seconddirection, as described herein. Further, or instead, the seconddirection may be, for example, substantially opposite the firstdirection across the volume such that the steps are generally performedthrough back-and-forth movement of hardware, as described herein.

Powder Dispensing

Referring again to FIGS. 1A, 1B, and 2 , in some implementations, thehopper 116 may include a plurality of dispensing rollers 146 along thedispensing region 118. The dispensing rollers 146 may be spaced apartfrom one another to define a gap. Each dispensing roller 146 may besubstantially cylindrical, which may be useful for defining the gap witha constant width. In general, the dispensing rollers 146 may rotaterelative to one another to meter and direct the powder 120 through thegap and toward the volume 108 in advance of movement of the spreader 114over the volume 108. Continuing with this example, the spreader 114 maymove over the powder 120 to form a substantially uniform layer of thepowder along the top of the volume 108, and the binder 112 may bedelivered onto this layer from the at least one ejection orifice 202 ofthe print carriage 106 as the print carriage trails the spreader 114over the volume 108. This process may be performed in differentdirections as necessary to carry out any one or more of themulti-directional binder jetting techniques described herein. Thus, ingeneral, the dispensing rollers 146 may be useful for addressing thechallenge of accurately dispensing the powder 120 in front of thespreader 114 as the hopper 116 and the spreader 114 move across thevolume 108 as part of a rapid binder jetting process and, morespecifically, a multi-directional binder jetting process.

In certain implementations, the dispensing region 118 may span adimension of the volume substantially parallel to the gap defined by theplurality of dispensing rollers 146 as the hopper 116 moves over thevolume 108. Continuing with this example, the plurality of dispensingrollers 146 may span this dimension of the volume 108 as the hopper 116moves over the volume 108 such that the powder 120 may be substantiallyevenly distributed along the dimension. Such a substantially evendistribution may, in turn, facilitate forming a substantially eventhickness of the layer formed as the spreader 114 pushes the distributedpowder 120 along the volume 108. As should be appreciated, improvedcontrol of layer formation may manifest as improved dimensional accuracyof the three-dimensional object 110 and, ultimately, as improved qualityof a final part formed from the three-dimensional object 110.

In certain implementations, the plurality of dispensing rollers 146 maybe substantially identical to one another, which may be useful forfacilitating consistent and even distribution of the powder 120. Thus,for example, each dispensing roller 146 have a substantially similardiameter. With such similar diameters, rotating each dispensing roller146 at the same rate may direct the powder 120 in a directionsubstantially perpendicular to a plane defined by a top of the volume108. This may be useful, for example, for reducing the likelihood ofproducing errant particles that may interfere with other aspects forformation of the three-dimensional object. Further, or instead, eachdispensing roller 146 may have the same surface finish, which may beuseful for increasing the likelihood that the dispensing rollers 146 maywear at substantially the same rate.

In certain implementations, the hopper 116 may include at least onerotational motor 148 coupled to one or more of the dispensing rollers146 and actuatable to rotate the plurality of dispensing rollers 146relative to one another. The at least one rotational motor 148 may beany of various different known types of motors arranged for providingrotational motion transmittable to the dispensing rollers 146. Thus, forexample, the at least one rotational motor 148 may include a rotaryactuator.

In certain instances, the at least one rotational motor 148 may becoupled to the plurality of dispensing rollers 146 such that the atleast one rotational motor 148 is actuatable to rotate the plurality ofdispensing rollers 146 in a counter-rotating direction relative to oneanother. In one direction, the counter-rotation may be useful forimparting a force to the powder 120 in the gap to expel the powder 120from the dispensing region 118. Continuing with this example, eachinstance of the dispensing roller 146 may be counter-rotated atsubstantially the same rotation speed (albeit in different directions),which may be useful for directing the powder 120 in a directionsubstantially perpendicular to a plane defined by the top of the volume108. In another direction of counter-rotation, the counter-rotation maybe useful for reducing inadvertent movement of the powder 120 throughthe gap.

The at least one rotational motor 148 may be in electrical communicationwith the controller 140 to control speed and direction of rotation ofthe at least one rotational motor 148 and, in turn, to control speed anddirection of rotation of the plurality of dispensing rollers 146. Thatis, in general, rotation of the plurality of dispensing rollers 146 maybe coordinated with one or more other aspects of the additivemanufacturing system 100. For example, rotation of the plurality ofdispensing rollers 146 may be adjusted in response to one or morechanges in parameters associated with the additive manufacturing system100, with such adjustments being useful for maintaining an advantageousdistribution of the powder 120 throughout varying conditions that may beencountered as the three-dimensional object 110 is formed. For example,the controller 140 may be configured to actuate the at least onerotational motor 148 based on movement of the hopper 116 over the volume108. Continuing with this example, the controller 140 may deactivate theat least one rotational motor 148 when the hopper 116 is not over thevolume 108. Such selective actuation of the at least one rotationalmotor 148 may reduce the likelihood of inadvertently dispensing thepowder 120 away from the volume 108 which, in turn, may reduce formationof errant particles of the powder 120. Additionally, or alternatively,the controller may be configured to actuate the at least one rotationalmotor 148 in a first direction of movement of the hopper 116 over thevolume 108 and to pause actuation of the at least one rotational motor148 in a second direction of movement of the hopper 116 over the volume,with the second direction being different from (e.g., opposite) thefirst direction.

In certain implementations, the controller 140 may be configured toactuate the at least one motor based on speed of movement of the hopper116 over the volume 108. Such a variation in speed may be useful, forexample, for driving the plurality of dispensing rollers 146 to controla rate of ejection of the powder 120 through the gap. Thus, for example,as the hopper 116 moves over the volume 108 at a higher rate of speed,the controller 140 may adjust actuation of the at least one rotationalmotor 148 to increase the angular speed of the plurality of dispensingrollers 146. In turn, this increase in angular speed may produce anincrease in the amount of powder 120 ejected from the dispensing region118. Thus, continuing with this example, the amount of powder 120dispersed in front of the spreader 114 may be adjusted to keep pace withincreases or decreases in speed of movement of the spreader 114 over thevolume 108.

In some instances, the position of the shutter 129 with respect to thedispensing region 118 may be controlled based at least in part onrotation of the plurality of the dispensing rollers 146. For example,shutter 129 may be selectively movable between a first (open) positionaway from the dispensing region 118 to a second (closed) position belowthe dispensing region 118 (to interrupt movement of powder exiting thehopper 116 via the dispensing region 118), with such movement based atleast in part on rotation of the plurality of dispensing rollers 146.That is, as the at least one rotational motor 148 is deactivated tocease rotation of the plurality of dispensing rollers 146, the shutter129 may move to the closed position to interrupt movement of the powder120 through the dispensing region 118.

FIG. 4 is a flowchart of an exemplary method 400 of dispensing powder inadditive manufacturing. In general, unless otherwise specified or madeclear from the context, the exemplary method 400 may be carried outusing any one or more of the additive manufacturing systems describedherein. Thus, for example, one or more steps of the exemplary method 400may be carried out by the additive manufacturing system 100 (FIG. 1A).Additionally, or alternatively, unless otherwise indicated or made clearfrom the context, the exemplary method 400 may be carried out as part ofa single-direction binder fabrication process, a multi-direction binderfabrication process, or a combination thereof

As shown in step 402, the exemplary method 400 may include moving ahopper over a volume defined by a print box. In general, such movementof the hopper over the volume may include any one or more of the variousdifferent techniques for moving a hopper over a volume as describedherein. Thus, unless otherwise specified or made clear from the context,moving the hopper over the volume may include any manner and form ofmoving the hopper 116 (FIG. 1A) over the volume 108 (FIG. 1A).

As shown in step 404, the exemplary method 400 may include, as thehopper moves over the volume, rotating a plurality of dispensing rollersdisposed along a dispensing region defined by the hopper. The rotationof the plurality of dispensing rollers may move a powder toward thevolume from the dispensing region. In this way, the powder may bedistributed along a top of the volume, where the powder may be spread toform a layer.

In general, rotation of the plurality of dispensing rollers may move thepowder toward the volume through a gap defined between the plurality ofdispensing rollers according to any one or more of various differentarrangements described herein. Thus, for example, the gap and thedispensing region may span a dimension of the volume substantiallyperpendicular to a direction of movement of the hopper over the volume.Additionally, or alternatively, rotating the plurality of dispensingrollers may include counter-rotating dispensing rollers of the pluralityof dispensing rollers. In certain instances, rotating the plurality ofdispensing rollers may include controlling a rotation speed of at leastone of the dispensing rollers of the plurality of dispensing rollersbased on a speed of movement of the hopper over the volume. Further, orinstead, rotating the plurality of dispensing rollers may includecontrolling a rotation speed of at least one of the dispensing rollersof the plurality of dispensing rollers based on a position of the hopperover the volume. As a more specific example, controlling the rotationspeed of the at least one of the dispensing rollers may include reducingthe rotation speed of the at least one of the dispensing rollers as thehopper moves from a first side of the volume to a second side of thevolume, the second side opposite the first side. Still further orinstead, rotating the plurality of dispensing rollers may includerotating each dispensing roller of the plurality of dispensing rollersat substantially the same rotation speed and, in certain instances, in acounter-rotating fashion. In some implementations, rotating theplurality of dispensing rollers may include controlling a rotation speedof each dispensing roller of the plurality of dispensing rollers basedon a direction of movement of the hopper over the volume (e.g.,activating rotation in one direction of movement and deactivatingrotation in another direction of movement).

As shown in step 406, the exemplary method 400 may include spreading thepowder along the volume to form a layer of the powder. As should beappreciated, the uniformity of this layer of the powder may be functionof uniformity of distribution of the powder ahead of the spreader instep 404. In general, spreading the powder along the volume may becarried out according to any one or more of the spreading techniquesdescribed herein.

As shown in step 408, the exemplary method 400 may include, in acontrolled two-dimensional pattern, ejecting a binder from at least oneejection orifice of a print carriage to the layer of the powder to forma portion (e.g., a two-dimensional slice) of the object. Thedistribution of the binder in this way may be carried out according toany on or more binder distribution techniques described herein.

As shown in step 410, the exemplary method 400 may include repeating oneor more of the steps of moving the hopper (step 402), rotating theplurality of dispensing rollers to dispense a powder (step 404),spreading the powder to form a layer along the volume (step 406), andejecting a binder to the layer in a controlled two-dimensional pattern(step 408) to form the object layer-by-layer.

Powder Packing

Referring again to FIGS. 1A, 1B, and 2 , in certain implementations, oneor more instances of the spreader 114 associated with the first materialcarriage 104 a and the second material carriage 104 b may be actuatableto vibrate at a frequency (e.g., a predetermined frequency) to transmitvibration from the spreader 114 to the powder 120 as the spreader 114moves across the volume 108. Such transmission of vibration may beuseful, for example, for packing the powder 120 in the volume 108 as thespreader 114 spreads the powder 120 to form a layer. In turn, such animprovement in packing of the powder 120 may improve quality of thefinal part formed from the three-dimensional object 110 (e.g., reducinglayer-to-layer variations of the powder 120 and/or improving densitycharacteristics of the three-dimensional object 110 being formed). Thus,as fabrication techniques increase in speed, the transmission ofvibration from the spreader 114 to the powder 120 may facilitatemaintaining or, in some cases, improving quality of the final partsformed from respective instances of the three-dimensional object 110.

As indicated above, the spreader 114 may include a roller and any of thevarious different vibration techniques described herein may be appliedto implementations of the spreader 114 including the roller. Thus, forthe sake of clarity and efficient explanation, the following discussionof vibration of the spreader 114 shall be understood to be applicable toimplementations in which the spreader includes a roller. However, unlessotherwise specified or made clear from the context, certain aspects ofvibration of the spreader 114 shall be understood to be applicable toother shapes.

Returning to the example in which the spreader 114 may be rotatable in adirection counter to a direction of movement of the roller across thevolume 108 as the roller moves across the volume 108, the spreader 114may be actuatable to vibrate as the spreader 114 is rotated in adirection counter to the direction of movement of the spreader 114 suchthat the vibration of the spreader 114 is superimposed on the counterrotation of the spreader. In general, the spreader 114 may be vibratedat a frequency that does not interfere with the overallcounter-rotational movement of the spreader 114. For example, as thespreader 114 is counter rotated, a high frequency rotational vibrationmay be superimposed on the spreader 114 as the spreader 114 continues tomove in a motion that is, overall, a counter-rotating motion.

In general, the additive manufacturing system 100 may include anactuator 150 coupled to the spreader 114. The actuator 150 may impartrotation (e.g., counter rotation) to the actuator and, further orinstead, may impart vibration to the spreader 114 according to any oneor more of various different techniques. In certain applications, theactuator 150 may vibrate the spreader 114 according to any of variousdifferent techniques suitable for imparting to the spreader 114 avibration having a frequency of greater than about 1 kHz and less thanabout 1 MHz. As an example, the actuator 150 may include an eccentricmotor coupled to the spreader 114 to impart vibration. Additionally, oralternatively, the actuator 150 may include one or more springs coupledto the spreader 114. Continuing with this example, vibration may beimparted to the spreader 114 through force applied to the one or moresprings. Further, or instead, the actuator 150 may include a voice coilactuator coupled to the spreader 114 such that actuation of the voicecoil actuator may transmit vibration to the spreader 114 at apredetermined frequency. In certain instances, the spreader 114 mayinclude a piezoelectric coating in electrical communication with theactuator 150, and the actuator 150 may pulse the piezoelectric coatingto impart vibration to the spreader 114. Further, or instead, thespreader 114 may include a wall defining a roller volume, and theactuator 150 may include a pump in fluid communication with a source ofa fluid (e.g., a gas such as air or a liquid such as water) and theroller volume of the spreader 114. In use, the pump may be actuated toprovide pressurized pulses of the fluid to the roller volume of thespreader 114. In response to such pressurized pulses, the wall of thespreader 114 may flex at the frequency of the pulses.

FIG. 5 is a flowchart of an exemplary method 500 of packing powder foradditive manufacturing. In general, unless otherwise specified or madeclear from the context, the exemplary method 500 may be carried outusing any one or more of the additive manufacturing systems describedherein. Thus, for example, one or more steps of the exemplary method 500may be carried out by the additive manufacturing system 100 (FIG. 1A).Additionally, or alternatively, unless otherwise indicated or made clearfrom the context, the exemplary method 500 may be carried out as part ofa single-direction binder fabrication process, a multi-direction binderfabrication process, or a combination thereof.

As shown in step 502, the exemplary method 500 may include moving atleast one roller across a volume defined by a powder box, with themovement of the at least one roller across the volume spreading a layerof a powder across the volume. In general, the layer of the powder maybe spreader across the entire volume as the at least one roller movesacross the volume. As an example, the at least one roller may includethe spreader 114 (FIG. 1A) implemented as a roller as described herein.As a specific example, moving the at least one roller across the volumemay include rotating the at least one roller in a direction counter tothe direction of movement of the at least one roller, which may beuseful for facilitating spreading the powder. Additionally, oralternatively, moving the at least one roller across the volume mayinclude moving the at least one roller at a predetermined frequencyacross the volume defined by the powder box.

As shown in step 504, the exemplary method 500 may include, as the atleast one roller spreads the layer of the volume, vibrating the at leastone roller to pack the powder in the volume. The vibration may beimparted to the at least one roller in any one or more of variousdifferent directions, as may be useful for achieving suitable packingcharacteristics of the powder. Thus, returning to the example of thecounter-rotating roller, vibrating the at least one roller may includesuperimposing rotational vibration of the at least one roller onto therotation of the at least one roller, as described herein. Further, orinstead, vibrating the at least one roller may include vibrating the atleast one roller in a direction substantially perpendicular to adirection of movement of the at least one roller across the volume.

In general, vibrating the at least one roller may include impartingvibration to the roller according to any one or more of the variousdifferent techniques described herein. Thus, for example, vibrating theat least one roller may include any one or more of the followingtechniques: delivering spring force to the at least one roller via oneor more springs coupled to the at least one roller; controlling aneccentric motor to a predetermined rotation speed as the eccentric motoris mechanically coupled to the at least one roller; actuating a voicecoil actuator at a predetermined frequency as the voice coil actuator ismechanically coupled to the at least one roller; delivering pulsedpneumatic force to a hollow volume of the at least one roller;electrically actuating a piezoelectric coating on the at least oneroller. Additionally, or alternatively, vibrating the at least oneroller may include vibrating the at least one roller at a frequency ofgreater than about 1 kHz and less than about 1 MHz.

In certain implementations, the frequency of vibration of the at leastone roller may be based on one or more characteristics of the powder.Such characteristics may include, for example, size distribution and/orcomposition of the powder. For example, vibrating the at least oneroller may include vibrating the at least one roller at a predeterminedfrequency corresponding to a wavelength substantially equal to anaverage size of particles of the powder as the at least one roller movesacross the powder box at the predetermined velocity.

As shown in step 506, the exemplary method 500 may include delivering abinder from the print carriage to the layer of the powder in apredetermined two-dimensional pattern associated with the layer as theprint carriage moves over the volume. Delivering the binder from theprint carriage in this way may include any manner and form of deliveryof the binder 112 (FIG. 1A) described herein.

As shown in step 508, the exemplary method 500 may include, for eachlayer of a plurality of layers, repeating one or more of the steps ofmoving the at least one roller across the volume (step 502), vibratingthe at least one roller (step 504), and delivering the binder (step 506)from the print carriage to the respective layer in a predeterminedtwo-dimensional pattern associated with the respective layer to form athree-dimensional object. Unless otherwise specified or made clear fromthe context, it should be generally understood that one or more of thesteps of the exemplary method 500 may be carried out as part of asingle-direction fabrication process or a multi-direction fabricationprocess. Thus, for example, the steps of moving the at least one rolleracross the volume (step 502), vibrating the at least one roller (step504), and delivering the binder from the print carriage (step 506) tothe respective layer may be carried out in a first direction across thevolume and in a second direction across the volume, with the seconddirection being different from the first direction.

While certain implementations have been described, other implementationsare additionally or alternatively possible.

For example, while additive manufacturing systems have been described asdelivering a powder, it should be generally understood that the powdermay have any of various different compositions useful for forming thethree-dimensional object into a dense part having a desired composition.Thus, for example, the powder in a given hopper may include any one ormore of various different materials that may be usefully combined toform a dense part. As a more specific example, the powder may includeany one or more of various different metals alloyable or otherwisecombinable with one another according to a predetermined materialspecification.

As another example, while additive manufacturing systems have beendescribed as delivering the same powder from multiple hoppers, it shouldbe appreciated that such description has been for the sake of clarity ofexplanation. More generally, each hopper may be associated with a uniquepowder. That is, in certain instances, a first powder in a first hoppermay have a first size distribution, and a second powder in a secondhopper may have a second size distribution, different from the firstsize distribution. Further, or instead, a first powder in a first hoppermay have a first composition (e.g., different types of particles,different concentrations of particles, and combinations thereof), and asecond powder in a second hopper may have a second composition,different from the first composition.

For example, referring again to FIG. 3 , the exemplary method 300 may becarried out using a first powder and a second powder. This may beuseful, for example, for forming a three-dimensional object withalternating layers having corresponding alternating compositions. Thatis, with respect to step 302, in the first direction, spreading thelayer of powder may include dispensing a first powder from a firsthopper and, in the second direction, spreading the layer of the powdermay include dispensing a second powder from a second hopper. The firstpowder may include, for example, metal particles of a first metal, andthe second powder may include, for example, metal particles of a secondmetal, different from the first metal.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable fora particular application. The hardware may include a general-purposecomputer and/or dedicated computing device. This includes realization inone or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors or otherprogrammable devices or processing circuitry, along with internal and/orexternal memory. This may also, or instead, include one or moreapplication specific integrated circuits, programmable gate arrays,programmable array logic components, or any other device or devices thatmay be configured to process electronic signals. It will further beappreciated that a realization of the processes or devices describedabove may include computer-executable code created using a structuredprogramming language such as C, an object oriented programming languagesuch as C++, or any other high-level or low-level programming language(including assembly languages, hardware description languages, anddatabase programming languages and technologies) that may be stored,compiled or interpreted to run on one of the above devices, as well asheterogeneous combinations of processors, processor architectures, orcombinations of different hardware and software. In another aspect, themethods may be embodied in systems that perform the steps thereof, andmay be distributed across devices in a number of ways. At the same time,processing may be distributed across devices such as the various systemsdescribed above, or all of the functionality may be integrated into adedicated, standalone device or other hardware. In another aspect, meansfor performing the steps associated with the processes described abovemay include any of the hardware and/or software described above. Allsuch permutations and combinations are intended to fall within the scopeof the present disclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps thereof. The code may be stored in a non-transitory fashion ina computer memory, which may be a memory from which the program executes(such as random access memory associated with a processor), or a storagedevice such as a disk drive, flash memory or any other optical,electromagnetic, magnetic, infrared or other device or combination ofdevices. In another aspect, any of the systems and methods describedabove may be embodied in any suitable transmission or propagation mediumcarrying computer-executable code and/or any inputs or outputs fromsame.

The method steps of the implementations described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So, for example performing the step of X includes anysuitable method for causing another party such as a remote user, aremote processing resource (e.g., a server or cloud computer) or amachine to perform the step of X. Similarly, performing steps X, Y and Zmay include any method of directing or controlling any combination ofsuch other individuals or resources to perform steps X, Y and Z toobtain the benefit of such steps. Thus, method steps of theimplementations described herein are intended to include any suitablemethod of causing one or more other parties or entities to perform thesteps, consistent with the patentability of the following claims, unlessa different meaning is expressly provided or otherwise clear from thecontext. Such parties or entities need not be under the direction orcontrol of any other party or entity, and need not be located within aparticular jurisdiction.

It should further be appreciated that the methods above are provided byway of example. Absent an explicit indication to the contrary, thedisclosed steps may be modified, supplemented, omitted, and/orre-ordered without departing from the scope of this disclosure.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

1. A method of additive manufacturing of an object, the methodcomprising: moving a hopper over a volume defined by a print box; as thehopper moves over the volume, rotating a plurality of dispensing rollersdisposed along a dispensing region defined by the hopper, the rotationof the plurality of dispensing rollers moving a powder toward the volumefrom the dispensing region; spreading the powder along the volume toform a layer of the powder; and in a controlled two-dimensional pattern,ejecting a binder from at least one ejection orifice of a print carriageto the layer of the powder to form a portion of the object.
 2. Themethod of claim 1, wherein rotation of the plurality of dispensingrollers moves the powder toward the volume through a gap defined betweenthe plurality of dispensing rollers.
 3. The method of claim 2, whereinthe gap and the dispensing region span a dimension of the volumesubstantially perpendicular to a direction of movement of the hopperover the volume.
 4. The method of claim 1, wherein rotating theplurality of dispensing rollers includes counter-rotating dispensingrollers of the plurality of dispensing rollers.
 5. The method of claim1, wherein rotating the plurality of dispensing rollers includescontrolling a rotation speed of at least one dispensing roller of theplurality of dispensing rollers based on a speed of movement of thehopper over the volume.
 6. The method of claim 1, wherein rotating theplurality of dispensing rollers includes controlling a rotation speed ofat least one dispensing roller of the plurality of dispensing rollersbased on position of the hopper over the volume.